Which agents are known triggers for malignant hyperthermia (MH)?

• A. Non-depolarizing muscle relaxants only
• B. Opioids and benzodiazepines
• C. Local anesthetics used during regional blocks
• D. Inhaled volatile anesthetics and depolarizing muscle relaxants

Answer: (D)

Malignant hyperthermia occurs when susceptible individuals are exposed to agents that disrupt calcium regulation in skeletal muscle, provoking a rapid, uncontrolled hypermetabolic crisis. The classic triggers are inhaled volatile anesthetics (such as sevoflurane, isoflurane, desflurane, and others) and the depolarizing muscle relaxant succinylcholine. These agents cause an excessive release of calcium from the sarcoplasmic reticulum via the ryanodine receptor, leading to sustained muscle contraction, heat production, increased carbon dioxide, acidosis, and potential organ damage. Other drugs listed—non-depolarizing muscle relaxants, opioids, benzodiazepines, and local anesthetics used for regional blocks—are not known triggers of MH, making them non-contributory in triggering an MH episode under standard conditions. Therefore, inhaled volatile anesthetics and depolarizing muscle relaxants are the recognized triggers.